The deep waters of the East Pacific hold an unprepossessing treasure trove: potato-sized lumps of rock that contain valuable metals such as manganese, cobalt and copper. Turns out, such “manganese nodules” are home to another kind of goody: a species of sponge never before seen, researchers report online September 24 in Systematics and Biodiversity. These newly discovered nodule-dwellers may help scientists monitor the impact of future deep-sea mining.

Little is known about life in the abyssal depths of the ocean, 4,000 to 6,000 meters down. But the prospect of mining in those depths is looming: For example, the United Nation’s International Seabed Authority has granted 16 exploration contracts for mining manganese nodules. To track how mining will affect deep-sea ecosystems over time, scientists are eager to establish a baseline of existing biodiversity in regions such as the Clarion-Clipperton Zone (CCZ), an area in the eastern Pacific Ocean littered with the nodules.

The new sponge species may be the key to that baseline. Zoologist Swee-Cheng Lim of the National University of Singapore and colleagues examined samples of manganese nodules retrieved from the CCZ in 2015 that were covered in snow-white patches of sponge. Based on the sponges’ unusual star-shaped spicules — skeletal parts that support the sponge’s soft tissues — the team suspected they’d found a new species. DNA analyses confirmed it. Dubbed Plenaster craigi, this species’ proximity to the nodules may make it the perfect canary in the coal mine.